1. Technical Field
The present invention relates to a method applicable to CAD/CAM systems such as punch presses for checking whether or not tool positioning interferes with a pattern to be processed.
2. Background Art
In order to automatically create an NC program for a punch press, an operator is required to determine, as part of the input operation, the position of a tool relative to an image to be processed. In such a case, it is necessary to check whether any interference is caused by the positioning of the tool.
FIG. 8(A) of the accompanying drawings shows that a punch tool T is positioned on a line segment Ea of a closed outline pattern E displayed on a CRT monitor by the operator's input operation. When the tool T is positioned in the bay of the closed outline E as shown in FIG. 8(A), it is necessary to check whether or not the tool T interferes with adjacent line segments Eb and Ec.
There is a method of checking such interference: an operator touches the line segment Ea on which the tool T is positioned (subject line segment), and the adjacent line segments Eb and Ec using a pointing device or the like, as indicated by "x" in FIG. 8(A), to cause the interference check module of an automatic programming device to conduct a checking operation.
However, this method requires the operator to manually touch each and every desired line segment, so that a substantial amount of time is needed in case of very complicated pattern, hence causing programming to become laborious.
FIG. 8(B) shows another method, which requires the operator only to specify the subject line segment Ea. As the subject line segment Ea is specified, an automatic programming device scans all the way along the outline of the closed pattern E to identify the adjacent line segments Eb and Ec for the interference checking.
In CAD patterns, however, the record of each line segment is stored in the order of drawing sequence, and actual patterns are usually by far more complicated than the one shown in FIG. 8. More often than not, CAD patterns includes a single closed outline E (configuration line) and many other closed patterns inside the outline E (for the punching), thereby totaling thousands of line segment records, including those for drawing a tool picture. Therefore, a number of calculation steps are needed to identify (or reach) the adjacent line segments Eb and Ec. If an automatic programming device with an ordinary processing rate is used for this purpose, it takes tens of seconds to conduct the interference checking for a single line segment. This makes it impossible to put the above-described automatic interference-checking method into practical use.